Smartwatches for Detection of Atrial Fibrillation (AFib) in Secondary Prevention of Cryptogenic Stroke

Inclusion Criteria: * Implanted Event Recorder with telemedicinal function (e.g., Biotronik BioMon 3m ProMRI HomeMon or similar) * Cryptogenic stroke (within the last six month) after full standard evaluation: * Stroke detected by computed tomography (CT) or magnetic resonance imaging (MRI) that is not lacunar (lacunar is defined as a subcortical infarct in the distribution of the small, penetrating cerebral arteries whose largest dimension is ≤1.5 cm on CT or ≤2.0 cm on MRI diffusion images) * Absence of extracranial or intracranial atherosclerosis causing ≥50 percent luminal stenosis of the artery supplying the area of ischemia * No major-risk cardioembolic source of embolism (i.e., no permanent or paroxysmal atrial fibrillation, sustained atrial flutter, intracardiac thrombus, prosthetic cardiac valve, atrial myxoma or other cardiac tumors, high-grade mitral valve stenosis, recent (within four weeks) myocardial infarction, left ventricular ejection fraction \<30 percent, valvular vegetations, or infective endocarditis) * No other specific cause of stroke identified (e.g., arteritis, dissection, migraine, vasospasm, drug abuse) * No paroxysmal atrial fibrillation in 72h of in-hospital ECG-monitoring, including at least one Holter- ECG for 24 hours. * Cryptogenic TIA with definite cortical syndrome (aphasia, neglect or homonymous hemianopia) (within the last six month) after full standard evaluation (see above) * Age: ≥40 yrs. * At least one of the following risk factors: * CHA2DS2VASc score ≥4 * Atrial runs * Left atrial size \> 45mm * Left atrial appendage flow ≤ 0.2m/s * No contraindication for anticoagulant therapy after acute phase of stroke * Written informed consent by patient or authorized caregiver Exclusion Criteria: * Patient is not able to perform 1-lead ECG recording with smartwatch * Patient possesses no smartphone (iOS version ≥10.0 or Android) * Implanted pacemaker or cardioverter defibrillator (ICD) * Pregnancy and breastfeeding period